The present invention relates to the general field of making a fiber blank by three-dimensional (3D) weaving for fabricating a blade platform out of composite material for a fan of an aviation turbine engine.
Fan blade platforms for turbine engines, and in particular for turbojets, are arranged between the blades of the fan so as to extend an inlet cone of the fan. They serve in particular to define the inside of the annular air inlet passage into the fan, which passage is defined on the outside by a casing.
It is known to have recourse to composite materials for making various parts of an aviation turbine engine. Thus, a composite material part may be obtained by making a fiber preform and densifying the preform with a matrix. In the intended application, the preform may be made of glass, carbon, or ceramic fibers, and the matrix may be made out of an organic material (polymer), out of carbon, or out of ceramic.
For parts presenting a relatively complex geometrical shape, it is also known to make a fiber blank or structure as a single piece by 3D or multilayer weaving and to shape the fiber structure so as to obtain a fiber preform having a shape that is close to the shape of the part that is to be fabricated.
Proposals have thus already been made to use 3D weaving to make a fiber preform of π-shaped section for a platform. Such platforms with a π-shaped section comprising a base and two legs form stiffeners that extend from a face of the base and that serve to stiffen the platform so as to avoid any movement of the platform under the centrifugal force generated by the speed of rotation of the fan.
With such platforms, it has been found that the mere presence of stiffeners does not always give sufficient strength against centrifugal force. It has thus been found necessary to add a wall between the free ends of the stiffeners in order to form a closed box structure under the base of the platform so as to reinforce its strength. Unfortunately, that implies providing a covering on the stiffeners of the platform preform, which operation is difficult to perform because of the size of the fibers involved. Consequently, this operation can easily lead to a part being rejected.